Canadian Mineralogist Vol. 27, pp. 447-449 (1989) RITTMANNITE, A NEW MINERAL SPECIES OF THE WHITEITE GROUP FROM THE MANGUALDE GRANITIC PEGMATITE, PORTUGAL YVONNE MARZONI FECIA DI CaSSATa AND PAOLO ORLANDI Dipartimento di Scienze delta Terra, Universita di Pisa, Via S. Maria 53, 56126 Pisa, Italy mov ANNA VEZZALINI Istituto di Mineralogia Petrografia, Universita di Modena, Via S. Eufemia 19, 41100 Modena, Italy ABSTRACT la formule (Mno.S4Cao.47b.OlMn1.oo(FeI.~sMno.S6Mgo.29) r;2.oo(Al1.7sFeo.2s)r;2.oo(OHh.02(P04)4.8H20. Densite mesu- Rittmannite, a new mineral species, is the MnMnFe ree 2.81(1), et calculee pour Z = 2, 2.83. La rittmannite analog of whiteite. It was found in altered phosphatic "nod- est biaxe positive. CXmes1.622, (3eale 1.626, 'Yeale 1.654, 2 V roes wes" from the Mangualde granitic pegmatite, Portugal, 43(2)°; I'orientation de I'indicatrice optique est: Xllb, Z:e as very small (0.3 x 0.3 x 0.04 mm), pale yellow, tabu- + 7°. Aucun pleochroYsme n'a ete decele. Le nom honore lar, pseudohexagonal crystals forming aggregates of sub- M. Ie professeur Alfred Rittman (1893-1980), volcanolo- parallel individual crystals. It occurs on kryzhanovskite, gue de renommee mondiale qui a contribue au developpe- frondeIite, hureaulite and adularia. Rittmannite is ment de la mineralogie, la petrographie et la microscopie monoclixyc, space group P2la, a !5.01(4), b 6.89(3), e optique. 10.16(3) A, (3 112.82(25)°, V 968(4) A3. The strongest lines (Traduit par la Redaction) in the X-ray powder-diffraction pattern [d in A(Iob,)(hkl)] are: 9.38(8)(001), 4.69(m8)(002), 2.802(8)(222). Electron- Mots-eMs: rittmannite, groupe de la whiteite, phosphate, microprobe data lead to the composition: MgO 1.5, Al203 pegmatite granitique, Mangualde, Portugal, nouveIIe 1.3, CaO 3.3, FeO 10.4, Fez03 (calc.) 2.6, MnO 18.9, espece minerale. P20S 35.9, H20 (calc.) 19.7, total 103.6 wt. OJo, cor- responding to the formwa: (MnO.S4Cao.47h;!.oIMn!.oo (Fe1 :isMno.S6MgO.29h:2.oo(AI I.7sFeo.2sh:2.oo(OHh.o2 INTRODUCTION (P04)4.8H20. Dmeas 2.81(1) g/cm3, and Deale for Z = 2 is 2.83 g/cm3. Rittmannite is biaxial (+ ), with cxmeas1.622, During a systematic study of the phosphates from (3eale1.626. 'Yeale1.654 and 2 Vmeas43(2)°: the orientation the Mangualde granitic pegmatite in the viseu dis- of the optical indicatrix is: Xllb, Z:e + 7°. No pleochro- trict, Portugal (Marzoni Fecia di Cossato & Orlan- ism was observed. Rittmannite honors Prof. Alfred Ritt- di 1987), a few pale yellow pseudohexagonal crys- man (1893-1980), world-famous volcanologist, who con- tals were noted. The X-ray powder-diffraction tributed to the development of modern mineralogy, pattern was found not to correspond to that of any petrography and optical microscopy. known mineral species, although it resembles that of whiteite. Keywords: rittmannite, whiteite group, phosphate, granitic pegmatite, Mangualde, Portugal, new mineral species. Further mineralogical studies indicated that the mineral is a new manganese-iron-aluminum phos- phate belonging to the whiteite group. The new spe- cies was named rittmannite in honor of Prof. Alfred SOMMAIRE Rittmann (1893-1980), eminent scientific personali- ty, who became interested early in his career in miner- La rittmannite, nouvelle espece minerale, est l'analogue alogy, petrography and optical microscopy. Later he MnMnFe de la whiteite. Nous l'avons decouverte dans des nodwes alteres de phosphates dans la pegmatite granitique became a world-famous volcanologist known for his de Mangualde (portugal). EIIe forme de tres petits cristaux classification of volcanic rocks and for his studies tabulaires (0.3 x 0.3 x 0.04 mm) pseudo-hexagonaux on the connection between tectonic style and mag- jaune pale en essaims d'individus sub-paralleles. Elle recou- matic trends. He was also author of a novel hypothe- vre kryzhanovskite, frondelite, hureaulite et adulaire. La sis on the origin and the composition of the earth's rittmannite est monoclinique, groupe spatial P21 a, a core. ~5.01(4), b 6.89(3), e 10.16(3) A, (3 112.82(25)°, V968(4) The mineral and the name have been approved by A3. l,sestrois raies les plus intenses du cliche de poudre [d the Commission on New Minerals and Mineral en A(l)J"hkl)] sont: 9.38(8)(001), 4.69(m8)(002), 2.802(8)(222). Les analyses, obtenues par microsonde elec- Names, LM.A. The holotype material is preserved tronique, donnent: MgO 1.5, Al203 1.3, CaO 3.3, FeO in the Museo di Storia Naturale of Pisa (4760/89), 10.4, Fez03 (calcwe) 2.6, MnO 18.9, P20S 35.9, H20 (cal- and the cotype, in the Museo Civico di Storia cule) 19.7, total 103.6% (par poids), ce qui correspond it Naturale of Milano. 447 448 THE CANADIAN MINERALOGIST FIG. 1. Rittmannite crystals on massive adularia (SEM photo, 240x). OCCURRENCE mannite crystals, suggesting that rittmannite was the last to form in this sequence. Mangualde is located in the Viseu district in north- ern Portugal. Hercinian (post-Stephanian) granites PHYSICAL AND OPTICAL PROPERTIES were emplaced in mica schist and gneiss, which out- crop to the south of the village. A complex of zoned About ten crystals of rittmannite were found. They veins (up to 11 m thick) of pegmatite cuts the are small, tabular on (001), pseudohexagonal in granites. Starting from the granite, their zoning is shape, forming aggregates of subparallel individual as follows: an aplitic periphery (2 cm thick), a fine- crystals. The average crystal dimensions are grained pegmatite with abundant mica, quartz and 0.3 x 0.3 x 0.04 mm. Rittmannite crystals are trans- feldspar (20 cm thick), a coarse-grained pegmatite parent, very pale yellow, with a white streak and with smoky quartz, pink orthoclase and white vitreous lustre. The estimated Mohs hardness is 3.5. plagioclase (300-350 cm), a coarse-grained pegma- The cleavage, parallel to (001), is indistinct. The den- tite like the latter, bearing uraniferous micas, Li- sity is 2.81(1) g/cm3 measured using Clerici solu- Mn-Fe-bearing phosphates ("nodules") and Mn- tion; the calculated value is 2.83 g/cm3 for Z=2. oxides (800 em) (De Michele 1969). On the universal stage, in parallel light, rittman- Our samples come from phosphatic "nodules" of oniteis biaxial (+), and the orientation of the indi- one of the thicker veins within a two-tnica granite, catrix is Xllb, Z:c + 7°, with 2 V 43(2)°. The index which outcrops in the valley between Mangualde and of refraction parallel to [100], measured by compa- the hamlet of Mesquitela. rison with liquids of known index in white light, gives Rittmannite was found on two small (1 x 1x 1 cm) fJ' = 1.628. The birefringence on (001) is 0.006, so phosphate specimens, consisting of crystallized red- that exis 1.622. brown, skeletal kryzhanovskite, black needle-like According to Bonatti (1942), from these data, frondelite, pink vitreous hureaulite and white mas- exmeas is 1.622. fJcalc is 1.626, 'Ycalcis 1.654 and 2V calc sive adularia (Fig. 1). No mineral is present on ritt- is 42°. No pleochroism was observed. RITTMANNITE, A MEMBER OF THE WHITEITE GROUP 449 TABLE 1. X-RAY POWOER-OIFFRACTION OATA logy with the space group of the jahnsite-whiteite FOR RITTMANNITE series). The cell parameters a 15.01(4), b 6.89(3), c hk1 10.16(3) A, (3112.82(25)°, were determined from the ------------ --------- X-ray powder-diffraction data (Table 1), obtained using a Gandolfi camera (diameter 114.6 mm) with S 9.38 9.37 001 vw 6.22 6.16 110 FeKa radiation and the least-squares refinement pro- m 5.66 5.61 ill gram USGSLSE (Appleman & Evans 1973). m 4.93 4.91 211 m 4.85 4.85 202 mS 4.69 4.68 002 DISCUSSION mw 4.07 4.08 i12 w 3.962 3.964 212 From the general formula XM(I)M(2hM(3)2 w 3.888 3.873 012 mw 3.758 3.751 401 (OHMH20MP04)4' where X = Ca, Mn; M(I) = w 3.571 3.585 312 Fe, Mn, Mg; M(2) Fe,Mg,Mn; M(3) Al3+, m 3.530 3.507 402 = = m 3.458 3.458 400 Fe3+, Moore & Ito (1978) proposed a nomenclature m 3.274 3.294 411 for the complex jahnsite-whiteite series on the basis w 3.208 3.203 311 w 3.125 3.123 003 of site occupancies in the structure. In jahnsite, the vw 3.054 3.057 121 proportion of Fe3+ exceeds that of Al3+ in M(3); in vw 2.997 2.995 212 mw 2.957 2.957 403 whiteite, the proportion of Al3+ exceeds that of mw 2.896 2.899 401 Fe3+ in M(3). Moreover, in the whiteite group, the S 2.802 2.807 222 vw 2.758 2.759 320 end-members whiteite-(CaFe2+Mg) (type),whiteite- vw 2.687 2.697 512 (CaMn2+Mg) and whiteite-(Mn2+Fe2+Mg) are vw 2.607 2.608 113;122 m 2.558 2.567 510 defined by the distribution of cations over the sites m 2.344 2.342 004 X, M(I) and M(2). According to this scheme of clas- vw 2.084 2.084 331 w 1. 989 1. 990 sification, rittmannite is the (Mn2+Mn2+Fe2+) w 1. 965 1. 968 member of the whiteite group. Also, it is the first m 1.947 1.949 m 1.884 1.889 mineral of the series with Fe as a dominant compo- nent in the M(2) site.